The recent publicity and emphasis on the "information superhighway" has increased awareness and acceptance of the Internet as a mass communication media. This broad based recognition of the Internet as a viable media for communication and interaction across multiple networks has also created a large established user base built upon the Internet standardized protocols for interaction between computer networks.
The paradigm for the Internet is that of a client-server relationship where Internet clients (browsers) communicate with Internet servers. To provide greater access to the Internet the communication protocols and languages utilized by the clients and servers have become standardized. These protocols include the Hyper-Text Transfer Protocol (HTTP), which is the communication protocol used for communications between clients and servers, and the Transmission Control Protocol/Internet Protocol (TCP/IP) the TCP portion of which is the transport specific protocol for communication between computers or applications. Also standardized is the language in which clients and servers communicate which is called Hyper-Text Markup Language (HTML).
In the context of the World Wide Web client/server applications the client may be a web browser which acts as the user interface. The web browser sends user requests to the appropriate web server and formats and displays the HTML data returned from the web server. The web browser also evaluates the HTML data to determine if there are any embedded hyper-link statements in the HTML data which would require subsequent browser requests which would then be initiated by the browser. A web server acts as the server for the client and processes the web browsers requests and returns the requested response as an HTML data portion of a HTTP data stream.
The basic communication structure for an Internet based system is depicted in FIG. 1. In FIG. 1 a web browser 10 communicates with a web server 20 over a communication link 15. This communication link is typically a local area network connection, wide area network connection, a connection over telephone lines or a combination thereof. The web browser 10 communicates with the web server 20 using TCP/IP. For the majority of Internet communications a web browser communicates with a web server using the generic communication protocol HTTP which is transmitted between the web browser and the web server over the TCP/IP link between the web browser and the web server. The actual data transferred between the web browser 10 and the web server 20 are HTTP data objects (e.g. HTML data) as described above. The web server 20 may be a proxy which receives web browser communications from a number of web browsers and routes them to the appropriate server.
The popularity of the web browser/web server and their common information and transport protocols, HTML and HTTP, has lead to rapid acceptance of web technology as a universal interface for network access to information. Furthermore, because the protocols and language for communication between web browsers and web servers are standardized the communication protocols and language will be the same whether a user is using Netscape Navigator.TM., NCSA Mosaic.TM., WebExplorer.TM. or any other web browser as their web browser to access network information. Therefore, the large installed user base for web browsers combined with the connectivity of the Internet and the ease of writing web application servers using the HTTP defined Common Gateway Interface (CGI) make web technology very attractive for a large class of forms-based applications.
At the same time that the Internet was growing in popularity and acceptance, mobile computing was also increasing in popularity. The use of laptops, notebooks, Personal Digital/Communication Assistants (PDAs/PCAs) and other portable devices has lead to an increase in demands for wireless communications. Wireless wide area networks, cellular communications and packet radio, however, suffer from common limitations if used in a web context. The high cost per byte of communications, slow response time, low bandwidth and unreliability all hamper use of wireless technology for the stateless communication protocol of the World Wide Web. Also, because the web protocol is stateless the amount of data per request and the number of communication requests transferred over the wireless connection are larger than would be necessary if the communication were not self contained.
Furthermore, the underlying mechanisms and protocols of Web browsing were developed with a traditional network model in mind. These mechanisms were developed based on the tacit assumption that the computers involved were connected via high-bandwidth, inexpensive, reliable links. However, in contrast to a wired LAN or WAN environment, mobile links are typically low-bandwidth, costly, and unreliable. Some mobile connections are less burdensome than others--for example, a simple dialup modem is both faster and cheaper than packet radio--but all are dramatically slower than their LAN counterparts. Mobile connections are also less reliable: dropped connections are not uncommon due to signal degradation, blockage, and other problems. Thus, applications such as web browsers that were targeted for a LAN environment often perform very poorly in a network-constrained setting.
Furthermore, the mobile environment raises the issue of disconnected operation. Standard Web browsing--as well as many existing networked applications--assume that disconnection is a comparatively rare error case. Operations typically fail when the client is disconnected from the server.
Weak connectivity and the possibility of disconnection lead to yet a third aspect of the mobility problem: the dynamic nature of a user's connectivity. At different times, a single user may be strongly connected (LAN), weakly connected (cellular or other mobile link) or disconnected.
Several factors contribute to poor usability and reduced user productivity when using browsers in a resource-constrained or unreliable communication environment typified by wireless communication. First, the browser protocol is synchronous, which means that users must wait until a request completes before another request can be made. When the delay is long due to slow wireless transmission, congested Internet or intranet traffic, or overburdened Web servers, users may become frustrated and unproductive.
Second, the natural burstiness of the synchronous request/response scheme may become a significant problem over a slow link or over a time cost based link. Over a wired LEN, server response time is usually the primary concern, but in a wireless environment, bandwidth and latency are typically the dominating factors. (Latency on a packet radio network can be on the order of several seconds.) Third, the usual synchronous request/response model does not work at all in the face of voluntary or involuntary disconnection. If a request cannot be satisfied immediately, an error code is typically returned and the user must explicitly retry the request at a later time.
In light of the above discussion, a need exists for improvements in the web browser/web server operation in the mobile computing environment which may be characterized by varying levels of connection performance and reliability.